The present invention relates to lawn waste sweepers having a hopper for collecting debris swept from a lawn or related surface in which the airstream carrying the waste material is directed through a debris collection hopper and then back to a suction zone of the sweeper.
Vacuum sweepers adapted to collect lawn debris are known in the art. Such sweepers typically have an inlet nozzle or duct connected to the suction side of a blower. Lawn debris is pulled by the blower through the inlet and then discharged past the blower through a discharge duct and into a hopper. The debris settles to the bottom of the hopper and the air is typically vented into the air through screened openings in the top of the hopper. Although these systems are typically adequate for collecting lawn waste, the discharged air can produce a considerable dust cloud, particularly in dry conditions.
In street sweepers and the like it is known to circulate the airstream carrying the waste material through a filter and then back to the area in which the inlet is located to discharge the air in the vicinity of the nozzle or inlet. The air is discharged under pressure through a restricted orifice in the form of a jet to assist in loosening and lifting debris on the surface to be cleaned. For example, U.S. Pat. No. 5,457,848 to Miwa discloses a recirculating type cleaner in which the outlet is located within the region of the suction port. The outlet is constricted in such a manner that the air is discharged in the form of a jet to loosen debris on the surface to be cleaned. Such sweepers appear intended for use as street sweepers or the like in cleaning hard and flat surfaces such as roads and parking lots where dust control is not the primary concern, rather dislodging material stuck to the surface to be cleaned is the primary concern. However, use of a jet of air directed at the surface of a lawn or the like is likely to create an undesirable amount of dust which would overwhelm the intake capacity of the suction inlet such that the dust would be discharged into the atmosphere.
Other references show similarly sized duct work for the suction inlet and the air discharge outlet, wherein the inlet and outlet are mounted laterally on opposite sides of a suction hood or the like, such as with the sweeper shown in U.S. Pat. No. 4,099,290 to Hiszpanski.
There remains a need for a lawn waste vacuum sweeper which is effective at collecting a wide variety of lawn waste while reducing the amount of dust and particulate matter discharged into the atmosphere by the sweeper.